The present invention relates to embodiments of a vehicle controller that controls the brakes and a method for detecting vehicle movement during braking. More specifically, embodiments of a vehicle controller and a method for detecting a commercial truck or tractor vehicle being pulled out of the desired travel path are disclosed.
Trucks or tractors can be equipped with one or more automated braking systems, for example, an antilock braking system (ABS), an automatic slip reduction system (ASR), a roll stability control system (RSC) and/or an electronic stability control system (ESC) in order to stabilize the vehicle in critical driving situations. By means of electro-pneumatic devices, such as modulators, controlled by the automated braking system, the brake pressures at each wheel end are individually controlled such that a locking or a spinning of the wheels is avoided and vehicle directional instability is mitigated.
If an individual modulator at any wheel end of the truck or tractor traps air at the wheel end during a braking cycle and fails to exhaust the air, the truck or tractor may be pulled in the direction of that wheel end. Some automated braking systems, such as Electronic Braking Systems (EBS) have pressure sensors at each wheel end, which can detect a brake pressure present at the wheel end and compare the actual brake pressure to a desired brake pressure. However, more common systems have no pressure sensor available at the wheel end to monitor the performance of the wheel end modulator.
Trucks or tractors may also be equipped with an automated cruise control system (ACC), such as the Bendix® Wingman® active cruise with braking system or a collision mitigation system (CMT), such as the Bendix® Wingman® Advanced™ collision mitigation technology. An automated deceleration request from the ACC or CMT system is received by the automated braking system controller when the ACC or CMT system determines that the truck or tractor is advancing too closely to a target vehicle. The braking system controller can respond to the automated deceleration request by automatically applying all of the wheel end brakes on the truck or tractor simultaneously. Therefore, when a wheel end modulator fails to exhaust air, the wheel end modulator will maintain or increase the brake pressure when automated braking is engaged. The wheel end modulator may also fail to hold air during automated braking. In the situation described above, the truck or tractor can be pulled out of the desired travel path due to different pressures at each wheel end, causing instability.